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  • 1
    Publication Date: 2017-10-01
    Print ISSN: 2038-1719
    Electronic ISSN: 2038-1727
    Topics: Geosciences
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  • 2
  • 3
    Publication Date: 2021-03-04
    Description: The ground-motion median and standard deviation of empirical groundmotion prediction equations (GMPEs) are usually poorly constrained in the nearsource region due to the general lack of strong-motion records. Here we explore the use of a deterministic–stochastic simulation technique, specifically tailored to reproduce directivity effects, to evaluate the expected ground motion and its variability at a near-source site, and seek a strategy to overcome the known GMPEs limitations. To this end, we simulated a large number of equally likely scenario events for three earthquake magnitudes (Mw 7.0, 6.0, and 5.0) and various source-to-site distances. The variability of the explored synthetic ground motion is heteroscedastic, with smaller values for larger earthquakes. The standard deviation is comparable with empirical estimates for smaller events and reduces by 30%–40% for stronger earthquakes. We then illustrate how to incorporate directivity effects into probabilistic seismichazard analysis (PSHA). This goal is pursued by calibrating a set of synthetic GMPEs and reducing their aleatory variability (∼50%) by including a predictive directivity term that depends on the apparent stress parameter obtained through the simulation method. Our results show that, for specific source-to-site configurations, the nonergodic PSHA is very sensitive to the additional epistemic uncertainty that may augment the exceedance probabilities when directivity effects are maximized. The proposed approach may represent a suitable way to compute more accurate hazard estimates.
    Description: This work was supported by the project MASSIMO—Cultural Heritage Monitoring in Seismic Area, PON01/02710—coordinated by Istituto Nazionale di Geofisica e Vulcanologia (INGV) and funded by the Italian Ministry of Education, University and Research and by the Seismic Hazard Center of Istituto Nazionale di Geofisica e Vulcanologia (Centro per la Pericolosità Sismica [CPS]).
    Description: Published
    Description: 966-983
    Description: 5T. Modelli di pericolosità sismica e da maremoto
    Description: JCR Journal
    Keywords: seismogenic sources ; finite fault simulations ; near source ; directivity effects ; ground motion variability ; seismic hazard ; Southern Italy ; 04.06. Seismology ; 05.06. Methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2020-10-22
    Description: The geometry of seismogenic sources could be one of the most important factors concurring to control the generation and the propagation of earthquake-generated tsunamis and their effects on the coasts. Since the majority of potentially tsunamigenic earthquakes occur offshore, the corresponding faults are generally poorly constrained and, consequently, their geometry is often oversimplified as a planar fault. The rupture area of mega-thrust earthquakes in subduction zones, where most of the greatest tsunamis have occurred, extends for tens to hundreds of kilometers both down dip and along strike, and generally deviates from the planar geometry. Therefore, the larger the earthquake size is, the weaker the planar fault assumption become. In this work, we present a sensitivity analysis aimed to explore the effects on modeled tsunamis generated by seismic sources with different degrees of geometric complexities. We focused on the Calabrian subduction zone, located in the Mediterranean Sea, which is characterized by the convergence between the African and European plates, with rates of up to 5 mm/yr. This subduction zone has been considered to have generated some past large earthquakes and tsunamis, despite it shows only in-slab significant seismic activity below 40 km depth and no relevant seismicity in the shallower portion of the interface. Our analysis is performed by defining and modeling an exhaustive set of tsunami scenarios located in the Calabrian subduction and using different models of the subduction interface with increasing geometrical complexity, from a planar surface to a highly detailed 3D surface. The latter was obtained from the interpretation of a dense network of seismic reflection profiles coupled with the analysis of the seismicity distribution. The more relevant effects due to the inclusion of 3D complexities in the seismic source geometry are finally highlighted in terms of the resulting tsunami impact.
    Description: Unpublished
    Description: New Orleans
    Description: 1T. Deformazione crostale attiva
    Description: 5T. Modelli di pericolosità sismica e da maremoto
    Keywords: tsunami ; seismic source geometry ; 03.03. Physical ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 5
    Publication Date: 2019-12-05
    Description: The response of continental forelands to subduction and oblique collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite-verging chains, however, is not very common and poorly understood. The Apulia block, at the southern end of the Adria microplate, Central Mediterranean, represents one of these latter cases, being the common foreland of the Dinarides and Apennines orogens. In its southern part, the Apulian foreland has preserved the Mesozoic paleomargin at the transition with the old oceanic Ionian crust that conversely underwent subduction under the Calabrian and Hellenic arcs. For these reasons, Apulia represents an interesting and rare case of study where double orogens and subduction have interacted with the foreland block. As described by various authors, the almost symmetrical bending of the Apulia foreland due the opposite load of the adjacent chains, produced a system of NW-SE trending normal faults. The precise age and the role of these faults have not been yet determined due to the lack of available information. In this contribution we investigated the internal deformation of the Apulia foreland using geophysical data at various resolutions and scales over a wide area. We used multichannel seismic profiles, part of which are provided in the collaborative framework between Spectrum Geo and INGV, recorded up to 12 s and provide a consistent imaging of the upper crustal setting of the Apulia foreland. High-resolution multichannel seismic profiles, multibeam high-resolution bathymetry and CHIRP profiles recently acquired by R/V OGS Explora provide constraints on the recent activity of the major fault systems identified. The analysis of this multiscale dataset highlights the presence and the role of a major NW-SE oriented active fault system which obliquely cuts the Apulia foreland. The presence of this fault system has already been hypothesized based on sparse seismic profiles, but its lateral continuity has never been documented. From the seismic viewpoint, this structure lies in a relatively silent area. Nonetheless, it hosts the 1743 Southern Apulia Mw 6.8 earthquake which widely damaged the Salento (S-Italy) and Ionian Islands (Greece) regions and whose source is still a matter of debate. This new geophysical dataset allowed us to reconstruct the 3D geometry of this fault system, whose architecture suggests a transtensive kinematics, and to analyse the syn-tectonic basins associated with the major faults which recorded the Late Quaternary to Holocene deformation. This work is being developed in the frame of the project “FASTMIT”, funded by the Italian Ministry of University and Research.
    Description: Unpublished
    Description: La Valletta, Malta
    Description: 2TR. Ricostruzione e modellazione della struttura crostale
    Keywords: Active Tectonics ; Marine Geology ; 04.04. Geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 6
    Publication Date: 2020-05-27
    Description: On 24 August 2016 a Mw 6.0 earthquake marked the beginning of a severe seismic sequence that struck Central Italy. This shock was followed by a Mw 5.9 on 26 October, by a Mw 6.5 on 30 October, by two Mw 5.4 aftershocks and by over 30,000 smaller shocks. Based on the widespread occurrence of surface breaks the majority of workers agreed that this sequence was caused by a widely-recognized system of Quaternary normal faults crossing the region, namely the Monti della Laga - Monte Vettore fault system. In this study we use surface and subsurface geological data, coupled with distributions of relocated seismicity and InSAR evidence of ground displacement, to show that the earthquake sequence was caused by the reactivation at depth of tectonic structures inherited from older tectonic phases combined with sympathetic slip along shallow ruptures. In particular we maintain that an inherited thrust fault is the most likely source of the 30 October, Mw 6.5 earthquake, the largest of the sequence. We also propose that the sequence involved slip along a normal fault partially located in the footwall of such thrust, and that this was the source of the 24 August, Mw 6.0 event. This latter fault partially reactivated the thrust in an extensional sense. The 26 October, Mw 5.9 event was caused by the extensional reactivation of an eastern portion of the same thrust; together with the 24 August earthquake this event triggered the reactivation of the whole thrust with extensional kinematics, ultimately leading to the Mw 6.5 shock. The 2016 sequence illuminates several aspects of the seismotectonics of the Central Apennines, casting doubts on a number of hypotheses that were put forward based exclusively on observations of exposed brittle structures. It also shows the key role of reactivated inherited structures as potential sources for large earthquakes, in addition to the activation of younger extensional fault systems.
    Description: Published
    Description: Vienna
    Description: 1T. Deformazione crostale attiva
    Keywords: Amatrice earthquake ; Norcia earthquake ; Geological cross-sections ; Seismotectonic model ; solid earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 7
    Publication Date: 2019-05-24
    Description: We adopted a multidisciplinary approach to investigate the seismotectonic scenario of the 30 October 2016, Mw 6.5, Norcia earthquake, the largest shock of the 2016-2017 central Italy earthquake sequence. First, we used seismological and geodetic data to infer the dip of the main slip patch of the seismogenic fault, that turned out to be rather low-angle (37°). To evaluate whether this is an acceptable dip for the main seismogenic source, we modeled earthquake deformation using single- and multiple-fault models deduced from aftershock pattern analyses. These models show that the coseismic deformation generated by the Norcia earthquake is coherent with slip along a rather shallow-dipping plane. To understand the geological significance of this solution we reconstructed the sub-surface architecture of the epicentral area. As the available data are not robust enough to converge on a single fault model, we built three different models encompassing all major geological evidence and the associated uncertainties, including the tectonic style and the location of major decollement levels. In all models the structures derived from the contractional phase play a significant role: from controlling segmentation to partially reusing inherited faults, to fully reactivating in extension a regional thrust, geometrically compatible with the source of the Norcia earthquake. Based on our conclusions, some additional seismogenic sources falling in the eastern, external portions of the Apennines may coincide with inherited structures. A circumstance that may be a common occurrence in this region of the chain, where the inception of extension is as recent as Middle-Upper Pleistocene.
    Description: This work was supported by INGV R.U. 0865.050, P.I. U. Fracassi, of Project MIUR-FISR 2016 “Centro di studio e monitoraggio dei rischi naturali dell'Italia centrale”, and by “Finanziamenti di Ateneo per Progetti Scientifici” - FRA 2015, P.I. L. Bonini. Petroleum Expert Ltd is acknowledged for making available the Move software to the to the University of Trieste.
    Description: Published
    Description: 990-1017
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: 2016 central Italy earthquake sequence ; geodetic inversion ; geological modeling ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2018-03-23
    Description: In the last decades, the calibration of reliable GMPEs became a critical issue in Probabilistic Seismic Hazard Assessment (PSHA). NGA-East project provides a set of new GMPEs for median and standard deviation of Ground Motions (GMs) and their associated weights in the logic trees for use in PSHA for Central and Eastern North-American Region. These results include the use of synthetic data to fill the lacking of observations, especially for moderate to large earthquakes in near field conditions. On the European side, some efforts have been made within the NERA EU Project for the calibration of physics-based GMPEs, which are particularly effective in showing important ground motion features in near source regions. Indeed, when the site is very close to the fault, the rupture processes are predominant and the finite-source effects, such as directivity, hanging wall/foot wall, radiation-pattern and slip distribution can dominate the GMs. Therefore, the empirical GMPEs are generally incapable to capture such features, because the strong motion recorded data in near source are few. This paper explains the aims of HYPSTHER (HYbrid ground motion prediction equations for PSha purposes: the study case of souTHERn Italy) project, devoted to develop a methodological approach to retrieve ground motion prediction models, based on the integration between recorded and synthetic data. The motivation of this research is to supply the lack of instrumental observations for moderate to large earthquakes in near fault conditions. In this framework, we will test this methodology for the study case of Southern Italy, focusing our attention on Calabria and Sicily regions. The target area has been chosen based on the expected high hazard level, despite the seismic activity has been scarce in the last decades. In addition, along the Sicily coast many critical infrastructures are present, such as chemical plants and large ports, which strongly increase the risk of technological accidents induced by natural hazards. The results of the HYPSTHER project will be a set of Ground Motion Prediction Equations (GMPEs) for PGA, PGV and SA in the period range T=0.04-4s. Additional results include recorded and synthetic ground motion datasets. The project products can be tested and incorporated in a next generation of the Italian Seismic Hazard Maps.
    Description: Published
    Description: Santiago Chile
    Description: 4T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Keywords: Hybrid GMPEs ; Earthquake simulation ; PSHA ; Southern Italy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 9
    Publication Date: 2018-03-20
    Description: Geometric complexities of subduction interfaces can be crucial for seismic and tsunami hazard studies because they may reveal important elements for constraining the dimension of future potential ruptures and even the location of asperities. Here we present the results of a recent work focused on the subduction interface of the Calabrian Arc where a remnant of the oldest oceanic crust in the world (280 Myr) forms a very narrow slab (~150 km). Historical and instrumental earthquake catalogues show no events that can be unequivocally assigned to the Calabrian subduction interface, nonetheless a significant in-slab seismicity below 40 km depth and a convergence rate of 1-5 mm/yr between the two involved plates (Africa and Europe) warn about the current activity of the subduction system and its possible seismogenic behaviour. Our 3D reconstruction of the Calabrian subduction interface (figure 1) merges a shallow part (〈20 km) based on the interpretation of ca. 9000 km of seismic reflection profiles (data provided by Spectrum Geo, collaborative framework with INGV CA-60), and a deeper part (20-350 km) reconstructed by analysing the seismicity distribution and the available tomographic data. The resulting model images several peculiar features that characterize the Calabrian subduction interface, such as an external shallow flat, a central ramp with lateral dip variations, and a deeper flat. The lateral terminations are characterized by the thrusting over the Apulian continental margin in the northern part and a Subduction Transform Edge Propagator fault system in the southern part. At 100-150 km depth the subduction is characterized by a slab breakoff. Geometric parameters that can be derived from the 3D model, such as the size and curvature of the interface, are often related to the seismogenic potential of subduction zones through empirical or model–driven scaling laws. In the case of the Calabrian subduction interface such fault scaling relations yield estimates of the maximum moment magnitude in the order of 8, if fully coupled.
    Description: TSUMAPS-NEAM, RITMARE, Porto Empedocle e PON MASSIMO Projects
    Description: Published
    Description: Lenzburg, Switzerland
    Description: 1T. Deformazione crostale attiva
    Description: 2T. Sorgente Sismica
    Description: 7T. Struttura della Terra e geodinamica
    Keywords: subduction interface ; 3D reconstruction ; seismic lines interpretation ; Calabrian Arc ; seismogenic sources ; 04.04. Geology ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 10
    Publication Date: 2019-02-01
    Description: The subduction of the Ionian oceanic crust under the Calabrian Arc is one of the major structural elements in the evolution of the central Mediterranean basin. The Calabrian subduction zone is characterized by a narrow slab that, in its south-western part, terminates on the Tindari-Alfeo Fault System (TAFS). This fault system represents a major NNW-SSE trending subduction-transform edge propagator (STEP) that plays an important role in the recent evolution of the Calabrian Arc. Thanks to a dense set of multichannel seismic reflection profiles with high penetration (up to 12 s), that allowed for a 3D reconstruction of the geological structures in the area, the TAFS results to presently be one of the best documented STEP systems in the world. We were able to characterize the geometrical arrangement, the timing of the deformation and the interplay between the Ionian lower plate and the upper-plate accretionary prism during the Plio-Quaternary. Our study highlights the presence of a mechanical decoupling between the lower plate and the upper plate. The Ionian oceanic (and/or transitional) crust in the lower plate hosts the master faults of the TAFS which do not propagate across the thick accretionary prism in the upper plate. This latter is affected by secondary deformation (bending-moment faulting, localized subsidence, stepovers, and restraining/releasing bends) associated to the activity of the TAFS at depth. The analysis of the secondary deformation in the upper plate, and in particular of the syn-tectonic Plio-Holocene basins, associated to the activity of the TAFS at depth, allow us to constrain the age of inception of the TAFS in the study area and to calculate the vertical component and the propagation rate of the deformation. Our findings highlight the mechanical behaviour that can be expected along major lithospheric boundaries that interact with previously formed structures and provide key elements to understand the significance of shallow geological structures with respect to the master faults at depth.
    Description: Published
    Description: La Valletta, Malta
    Description: 2TR. Ricostruzione e modellazione della struttura crostale
    Keywords: subduction ; seismic reflection profiles ; active tectonics ; 04.04. Geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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